1. Field of the Invention
This invention relates to keyboards having keys activated by electrical contacts, designed to provide for various commands depending on the state of the keys selected by the operator.
2. Summary of the Invention
Accordingly, it is the object of this invention to provide a novel keyboard with four possible states, employing a particularly simple electrical circuit, in dipole form, enabling simple individual reading of the four possible states.
Esssentially, this object and others are achieved according to the invention, the keyboard having keys activated by electrical contacts and the capacity to read one state from among four possible states, in which the keyboard is a dipole between the terminals of which three connectors are mounted in parallel, each including one of the electrical contacts, wherein two of these connectors are formed by diodes connected anode to cathode, whereby the various states may be discriminated by the successive application of two reverse electrical voltages to the terminals of the dipole and by means of corresponding logic detector.
In addition to its simple two-wire connection wiring, the keyboard of the invention advantageously employing only passive components, and lends itself to logic reading using simple components (such as selective current application transistors and logic state detection resistors) while, through its read element, it can tolerate relatively high parasitic resistance internal to the keyboard.